1. Field of the Invention
The present invention relates generally to electronic labeling and localizing, more particularly, to a method and apparatus for electronic labeling and localizing of items whose location may change.
2. Description of Related Art
Numerous methods and systems exist for establishing communication between two end points. While these known methods of communication allow for the transfer of information, they fail to provide an indication of the location of either end point.
Knowledge of an end point's location enhances the performance of communication systems. Specifically, as more and more applications are targeted for wireless communication, the cost of bandwidth will grow and the ability to reuse bandwidth will become necessary. Localizing an end point will allow the efficient reuse of bandwidth.
For example, localization of an end user of a mobile wireless communication system would allow bandwidth to be reused. A cellular system consists of a number of radio base stations connected to a mobile telephone switching office (MTSO). Each base station typically serves a given geographical area, or cell. The MTSO automatically switches connections between base stations as a mobile subscriber moves from one cell to another. In such an arrangement, frequencies allocated for use by one base station in a cell cannot be used by another base station in a neighboring cell because multiple signals at the same frequency would interfere with one another.
If the location of each mobile subscriber is known, however, then each base station would be provided with the information necessary to reuse frequencies and bandwidth. Knowing the locations of a first subscriber and a second subscriber would allow a base station to reuse the frequency allocated to the first subscriber when providing service to the second subscriber located in a different subregion of the same cell. Localization of both subscribers would allow the base station to determine when, based upon the available antenna directivity and signal attenuation, a specific frequency can be reused.
Localization of an end point in a communication system also enhances security. Typically, remote access to confidential information, such as credit card and bank account records and voice mail, is governed by personal identification numbers or other user-specific code. Unfortunately, such code can be lost or stolen, making unauthorized access possible. An unauthorized user merely needs to contact the system, identify the account, and provide the code.
Localization would augment the existing security measures. A user's account would have not only an associated identifying code, but also an associated identifying location from which remote access could be made. An attempt to access account information from an unauthorized location could result in denied access or the invocation of another level of security.
Industries having a large inventory of items would also benefit from the ability to quickly and efficiently localize a given end point. For example, a telecommunications company may have a warehouse of circuit packs, cables, couplers, receivers, and the like. In the past, locating a given circuit pack would entail keeping a record of that circuit pack's physical location in the inventory. Such a record may include information relating to a particular slot, in a particular cabinet, in a particular section of a warehouse. Even if the records are kept as part of an electronic database, this system has several disadvantages.
First, such a system is labor intensive. Each time an article is added to the inventory, its location must be manually noted and the database manually updated. Similarly, each time an article is removed from the inventory, the database must be updated by deleting the record so that no false indication of the item's presence is given. Furthermore, each time an item is moved, such as when making room for other articles in the inventory, its new location must be noted and the database updated. Thus, maintenance of the system is time-consuming.
Second, there is a potential for losing or misplacing an article because no means exists for automatically accounting for movement of the article. If an article in the inventory is moved and the operator fails to record the new location, there is no way for that article to be located. In a warehouse containing thousands of articles, even an exhaustive search of the warehouse would likely prove fruitless. Lost articles increase costs as they consume precious storage space and are, in essence, paid-for inventory that is unavailable for use.
There are systems within the generic class of communication systems that allow an operator to remotely communicate with an article in inventory. One type of system used in communicating with articles in an inventory is known as an Electronic Shelf Labeling (ESL) system. The ESL system comprises a central transmitter, which includes a centralized node for transmitting a modulated signal. The ESL also comprises a plurality of receivers for receiving the modulated signal, each receiver being associated with a different article. In operation, the central transmitter transmits a signal modulated with information particular to one or more given articles. While all articles receive the modulated signal, a demodulator and logic associated with each article allows only those articles identified by the information modulated into the first signal to respond. Those particular articles proceed to receive data from the central transmitter and, in turn, transmit a second signal that indicates to the central transmitter that the data has been received by the articles. The frequency of this acknowledge signal may be changed to a frequency higher than that of the modulated signal so that the central transmitter may better receive the acknowledge signal. By providing each article with a liquid crystal display, the ESL system may be used to display and update price information of items in a grocery store. Thus, although a level of communication is established between the central transmitter and a particular receiver, the ESL fails to provide information necessary to locate the particular receiver or associated article.
Additionally, power constraints would limit the utility of systems capable of communicating with an end point. Specifically, the end point that is to be communicated with typically has a limited power supply. Illustrative of the limitation of power consumption, items may remain in an inventory for years before use. Thus, any localizing system must be efficient and conserve power.